1. Field of the Invention
This invention relates to an upsetter for simultaneously upsetting a plurality of items or work pieces, and more particularly, to an upsetter which is capable of simultaneously upsetting a desired number of work items in spite of the existence of variations in volume between the individual work items to improve its productivity to a significant degree.
2. Description of the Prior Art
It is known in the art to employ an upsetter which is provided with a hydraulic cushioning mechanism to cope with variations in the volume of work items to be upset, as illustrated in FIGS. 1a to 3b. More specifically, in FIGS. 1a to 3b denoted at 1 is a split die set with a forming section, and at 2 a punch which is extractably protrudable into the forming section of the die set and which is, in the particular example shown, driven by a crank type punch drive mechanism 6 through a hydraulic cushioning mechanism 5 constituted by a hydraulic cylinder 3 and a pressurizing ram 4 fitted fluid-tightly in the cylinder 3. Reference numeral 7 indicates a pressure accumulator.
FIGS. 1a and 1b illustrate an upsetting operation of a single thin-walled pipe P, while FIGS. 2a and 2b an upsetting operation of a single thick-walled pipe P. Obviously, the operational efficiency or the productivity is lowered when work items of different volumes are upset separately in this manner.
In order to eliminate this difficulty, there has been proposed an upsetter as shown in FIGS. 3a and 3b, which is provided with a number of forming sections side by side in the split die set 1 and a corresponding number of punches 2 which are extractably protrudable into the respective forming sections for upsetting simultaneously a plurality of work items.
The upsetter of FIGS. 3 is capable of multiple upsetting operation as long as there is no difference in volume between the work items which simultaneously undergo the upsetting operation. However, simultaneous upsetting operation becomes difficult when there is a difference in volume as seen in FIG. 3b.